~ Connecting two Bluetooth headsets to your Linux system: audio routing in PipeWire

Imagine you want to stream a movie at home but also want to keep things quiet to avoid disturbing others. Evidently, this what headsets were invented for. Connecting one wireless Bluetooth headset is typically straightforward - aside from the occasional Bluetooth pairing issues. But what if you want to watch that movie with someone else, and you both want to use headsets? Connecting two Bluetooth headsets, or even combining wired and wireless headsets to share the same audio, isn’t as simple as it sounds. This blog post shows how to achieve this on modern Linux distributions.

Fig: Connecting an audio source - Spotify - to multiple output devices by using audio routing with PipeWire and `qpwgraph`.

During the last years, several Linux distributions have started to support the PipeWire audio server. It is even the default audio server in Debian 12 and Ubuntu 22.10. With PipeWire, managing audio devices has become much easier. PipeWire enables flexible audio setups and supports audio routing: sending out audio from a single source to several output devices. This is exactly what we need to stream audio to multiple headsets.

If you use PipeWire on your system, qpwgraph provides an intuitive graphical interface that lets you visualize and control audio routing. To connect multiple headsets:

1. First install qpwgraph e.g via apt install qpwgraph
2. Startup qpwgraph which should show your current audio routing graph.
3. Pair your Bluetooth headsets to your machine. They will appear in the audio routing graph once paired successfully.
4. Connect the audio source to your headsets by connecting ‘wires’ from your media player to the headsets.

I was surprised how robust audio has become on Linux and how easy and user friendly it is to set up even more complex audio / MIDI configurations. Give it a try!

0110.be and UGent

~ Validity and reliability of peak tibial accelerations as real-time measure of impact loading during over-ground rearfoot running at different speeds

The publication of this paper seemed an almost sisyphean task, but it is now finally in print after about four years since first submission. All’s well that ends well and it is well indeed: the paper contributes a fundamental insight around the resultant peak tibial acceleration (PTA) in forefoot running: contrary to what is often presumed, the resultant PTA is higher in forefoot running! The paper combines two separate experiments into a single analysis framework which ensures robustness in the finding. The conclusions of the article can be found below:

Conclusions Many coaches and practitioners presume that forefoot striking decreases impact severity and prevents overuse injuries; however, our data show that instructed and habitual forefoot strikes have greater resultant but not axial PTA than habitual rearfoot strikes in level running at a submaximal speed. The forefoot strikes had a sharp decrease in the antero-posterior velocity of the shank following touchdown and, therefore, a greater antero-posterior acceleration, which resulted in the greater resultant peak tibial acceleration compared to the rearfoot strikes. Conclusively, the foot strike pattern differently affected PTAs and should be taken into account when evaluating 3D impact severity in distance runners.

My contribution to the paper was limited to technical development and support during the measurements at Ghent University. For the full paper, please read the publishers version of Validity and reliability of peak tibial accelerations as real-time measure of impact loading during over-ground rearfoot running at different speeds.

UGent and Research papers